Hi the only problem that i can see with using one of these is that if your trap on the basin was to run dry, i.e. the water in it evaporates, you will get sewer gasses entering the building.......not good
You should fit a anti-syphon trap as well. just to be on the safe side.
The fact that the waste connection is horizontal shouldn't cause you a prolem as long as your waste runs down towards the pan connector